To send an Invoice: 

   1. Go over the Load;

   2. Click on View (down arrow); 

   3. Click on Invoice:

   4. Email Invoice. 

If the Invoice can not be sent check if there is customer's e-mail address and fax number. 

Fix it adding the e-mail address of the Customer to the CRM or go over the load and  click Edit and fill in the e-mail address or fax.